Flexible fuel compensation system

Abstract

A flexible fuel compensation system for an internal combustion engine. The flex-fuel system includes a method of run fuel pulsewidth calculation which controls the amount of fuel being sent to the fuel injectors. The method calculates multipliers to be used in calculating a first and second pulsewidth multiplier and fuel injector pulsewidths.

What is claimed is: 
     
       1. A method of calculating a pulsewidth for controlling fuel injection into an internal combustion engine, wherein a fuel injection control system of the internal combustion engine includes a microprocessor and a plurality of electronically controlled fuel injectors, the method comprising the steps of: calculating a plurality of multipliers for a pulsewidth calculation;   calculating a first and second pulsewidth multiplier;   calculating first and second fuel injector pulsewidth values;   adjusting a sensed manifold absolute pressure with the first and second fuel injector pulsewidth values;   storing a temporary fuel pulsewidth value;   calculating a manifold absolute pressure acceleration enrichment value;   recalculating the first and second fuel pulsewidth values;   storing the recalculated pulsewidth values to a first and second fuel pulsewidth values; and   controlling the plurality of electronically controlled fuel injectors using the recalculated pulsewidth values.   
     
     
       2. A method of calculating a pulsewidth for controlling fuel injection into an internal combustion engine, wherein a fuel injection control system of the internal combustion engine includes a microprocessor and a plurality of electronically controlled fuel injectors, the method comprising the steps of: determining if a vehicle is configured for alternative fuel;   calculating a plurality of multipliers for a pulsewidth calculation;   determining the position of a throttle;   calculating first and second pulsewidth multiplier values;   determining if a sensed engine speed is greater than a predetermined value;   adjusting a sensed manifold absolute pressure with the first and second fuel injector pulsewidth values;   storing a temporary fuel pulsewidth value;   calculating a manifold absolute pressure acceleration enrichment value;   recalculating the first and second fuel pulsewidth values;   storing the recalculated pulsewidth values to a first and second fuel pulsewidth values; and   controlling the plurality of electronically controlled fuel injectors using the recalculated pulsewidth values.   
     
     
       3. A method as set forth in claim 2 including the step of setting all alternative fuel multipliers equal to a predetermined value if the vehicle is not configured for alternative fuel. 
     
     
       4. A method as set forth in claim 2 wherein said step of calculating a plurality of multipliers for the pulsewidth calculation includes the steps of: calculating a coolant temperature based flexible fuel vehicle vaporization compensation multiplier;   calculating a coolant temperature and time from start based flexible fuel vehicle vaporization compensation multiplier;   calculating a flexible fuel vehicle fuel blend energy content compensation multiplier;   calculating a transient alternative fuel vehicle vaporization compensation multiplier;   calculating an alternative fuel vehicle pumping efficiency multiplier;   calculating a total alternative fuel pulsewidth multiplier;   calculating a fuel enrichment multiplier;   multiplying the fuel enrichment multiplier by a vaporization compensation multiplier;   calculating a second fuel enrichment multiplier as a function of coolant temperature if the throttle is at wide open throttle; and   calculating a second fuel enrichment multiplier as a function of the manifold absolute pressure and coolant temperature.   
     
     
       5. A method as set forth in claim 4 wherein said step of calculating a flexible fuel vehicle vaporization compensation multiplier includes the step of interpolating a flexible fuel vehicle vaporization compensation multiplier using coolant temperature and percent methanol as interpolation parameters. 
     
     
       6. A method as set forth in claim 4 wherein said step of calculating a flexible fuel vehicle vaporization compensation multiplier includes the step of interpolating the said multiplier from a set of calibration values using the coolant temperature and percent methanol as interpolation parameters. 
     
     
       7. A method as set forth in claim 4 wherein said step of calculating a transient fuel flexible fuel vehicle vaporization compensation multiplier includes the step of interpolating said multiplier from a set of acceleration enrichment pulsewidth values using the coolant temperature and percent methanol as interpolation parameters. 
     
     
       8. A method as set forth in claim 4 wherein said step of calculating a flexible fuel vehicle pumping efficiency multiplier includes the step of interpolating said multiplier from a flexible fuel vehicle pumping efficiency multiplier using the engine speed and percent methanol as interpolation parameters. 
     
     
       9. A method as set forth in claim 2 wherein said step of calculating a first and second pulsewidth multiplier includes the steps of: combining the fuel enrichment multipliers;   multiplying the combined value by a barometric enrichment compensation multiplier to obtain a first product;   multiplying said first product by an enrichment compensation multiplier to obtain a second product;   multiplying said second product by an air charge temperature enrichment compensation multiplier to obtain a third product;   multiplying said third product by a throttle lean out factor to obtain a fourth product;   multiplying said fourth product by a manifold absolute pressure lean out factor to obtain a fifth product;   multiplying said fifth product by a part throttle enrichment factor to obtain a base multiplier;   storing a copy of the said base multiplier; and   multiplying said base multiplier by an adaptive memory factor and an oxygen controller factor associated with a first bank of cylinders of the internal combustion engine to obtain a pulsewidth multiplier associated with the first bank of cylinders.   
     
     
       10. A method as set forth in claim 9 including the steps of: determining if the engine speed is above a predetermined value;   reloading the said base multiplier; and   multiplying said base multiplier by a Bank-2 adaptive memory factor and a Bank-2 oxygen controller factor to obtain a Bank-2 pulsewidth multiplier.   
     
     
       11. A method as set forth in claim 2 wherein said step of calculating a first and second fuel injector pulsewidth includes the steps of: determining if the throttle is at wide open throttle;   subtracting a wide open throttle manifold absolute pressure offset from the average manifold absolute pressure to obtain a first difference if the throttle is at wide open throttle;   multiplying said first difference by a wide open throttle K-factor and by a wide open throttle volumetric efficiency value;   subtracting a non-wide open throttle manifold absolute pressure offset from the average manifold absolute pressure to obtain a second difference if the throttle is not at wide open throttle;   multiplying said second difference by a non-wide open throttle K-factor and a non-wide open throttle volumetric efficiency value; and   adding a barometric compensation pulsewidth value to obtain a sum.   
     
     
       12. A method as set forth in claim 11 including the steps of: determining which cylinder bank the calculations are for;   multiplying said sum by the Bank-1 pulsewidth multiplier if the calculations are for cylinder Bank-1;   storing a product to a Bank-1 base fuel pulsewidth;   multiplying said sum by the Bank-2 pulsewidth multiplier if the calculations are for cylinder Bank-2; and   storing a product to Bank-2 base fuel pulsewidth.   
     
     
       13. A method as set forth in claim 2 wherein said step of adjusting a sensed manifold absolute pressure with a plurality of values includes the steps of: determining if the engine speed is less than a predetermined value;   determining if the throttle is at wide open throttle if the engine speed is less than a predetermined value;   determining if the throttle is at wide open throttle if the engine speed is less than a predetermined value;   subtracting a manifold absolute pressure offset value from an average manifold absolute pressure;   multiplying the difference of said subtracting by a K-factor and a volumetric efficiency value;   adding to the product of said multiplying step the barometric compensation pulsewidth value; and   multiplying the sum of said adding step by the Bank-1 or Bank-2 pulsewidth multiplier.   
     
     
       14. A method as set forth in claim 13 including the steps of: loading the Bank-1 or Bank-2 base fuel pulsewidth value into memory if the engine speed is not below a predetermined value; and   storing the fuel pulsewidth value to memory.   
     
     
       15. A method as set forth in claim 2 wherein said step of calculating a manifold absolute pressure acceleration enrichment value includes the steps of: calculating a manifold absolute pressure acceleration enrichment pulsewidth;   adding to the said calculating step a throttle acceleration enrichment pulsewidth;   multiplying the sum of said adding step by an acceleration enrichment decay multiplier and by an alternative fuel acceleration enrichment vaporization compensation multiplier;   adding to the product of said multiplying step the temporarily stored fuel pulsewidth value and an AIS enrichment pulsewidth to obtain a third sum; and   multiplying said third sum by a total alternative fuel pulsewidth multiplier.   
     
     
       16. A method as set forth in claim 15 including the steps of: determining which cylinder bank the calculations are for;   storing the product of said multiplying of said third sum step in the fuel pulsewidth associated with the second bank of cylinders if the calculations were for the second bank of cylinders; and   storing the product of said multiplying of said third sum step in the fuel pulsewidth associated with the first bank of cylinders if the calculations were for the first bank of cylinders.   
     
     
       17. A method as set forth in claim 9 wherein said step of multiplying said base multiplier by a Bank-1 oxygen controller factor includes the step of adding a plurality of constants including a percent methanol oxygen biasing trigger level, a rich primary limit percent methanol bias, a lean primary limit percent methanol bias, and a cell mask value to obtain a value for said oxygen controller factor. 
     
     
       18. A method of calculating a pulsewidth for controlling fuel injection into an internal combustion engine, wherein a fuel injection control system of the internal combustion engine includes a microprocessor and a plurality of electronically controlled fuel injectors, the method comprising the steps of: determining if a vehicle is configured for alternative fuel;   calculating a first flexible fuel vehicle vaporization compensation multiplier;   calculating a second flexible fuel vehicle vaporization compensation multiplier;   calculating a flexible fuel vehicle fuel blend energy content compensation multiplier;   calculating a transient fuel flexible fuel vehicle vaporization compensation multiplier;   calculating a flexible fuel vehicle pumping efficiency multiplier;   calculating a total flex-fuel pulsewidth multiplier;   calculating a second fuel enrichment multiplier;   multiplying said second fuel enrichment multiplier by the second vaporization compensation multiplier;   determining a position of a throttle;   calculating a coolant based fuel enrichment multiplier;   combining the said first and second fuel enrichment multipliers;   multiplying the value of said combining step by a barometric enrichment compensation multiplier and an enrichment compensation multiplier to obtain a first product;   multiplying said first product by an air charge temperature enrichment compensation multiplier and by a throttle lean-out factor to obtain a second product;   multiplying said second product by a manifold absolute pressure lean-out factor by a part-throttle enrichment factor and by a hot fuel enrichment factor to obtain a base multiplier;   storing a copy of the base multiplier to memory;   multiplying said base multiplier by an adaptive memory factor associated with a first bank of cylinders and by an oxygen controller factor associated with the first bank of cylinders to obtain a third product;   storing said third product to a Bank-1 pulsewidth multiplier;   determining if the said engine speed is greater than a predetermined value;   reloading said base multiplier from memory if the engine speed is not greater than a predetermined value;   multiplying said base multiplier by an adaptive memory factor associated with the second bank of cylinders and by an oxygen controller factor associated with the second bank of cylinders to obtain a fourth product;   storing said fourth product to a pulsewidth multiplier associated with the second bank of cylinders; and   controlling the plurality of electronically controlled fuel injectors using the recalculated pulsewidth values.   
     
     
       19. A method as set forth in claim 18 wherein said step of calculating a fuel injection pulsewidth includes the steps of: determining if the throttle is at wide open throttle;   subtracting a wide open throttle manifold absolute pressure offset from an average manifold absolute pressure value if the throttle is at wide open throttle to obtain a first difference;   multiplying said first difference by a wide open throttle K-factor and by a wide open throttle volumetric efficiency value to obtain a fifth product;   adding a barometric compensation pulsewidth value to said fifth product to obtain a first sum;   subtracting a non-wide open throttle manifold absolute pressure offset from said average manifold absolute pressure if the throttle is not at wide open throttle to obtain a second difference;   multiplying said second difference by a non-wide open throttle K-factor and a non-wide open throttle volumetric efficiency value to obtain a sixth product;   adding said barometric compensation pulsewidth value to said sixth product to obtain a second sum;   determining if the calculations are for the first or second bank of cylinders;   multiplying said first or second sum by the pulsewidth multiplier associated with the first bank of cylinders if the calculations are for the first bank of cylinders to obtain a base fuel pulsewidth associated with the first bank of cylinders; and   multiplying said first or second sum by the pulsewidth multiplier associated with the second bank of cylinders if the calculations are for the second bank of cylinders to obtain a base fuel pulsewidth associated with the second bank of cylinders.   
     
     
       20. A method as set forth in claim 18 including the steps of: determining if the engine speed is less than a predetermined value;   determining if the throttle is at wide open throttle;   subtracting a manifold absolute pressure offset from the average manifold absolute pressure to obtain a difference;   multiplying said difference by a K-factor and a volumetric efficiency value to obtain a product;   adding a barometric compensation pulsewidth value to said product to obtain a sum;   multiplying said sum by a pulsewidth multiplier to obtain a fuel pulsewidth;   storing fuel pulsewidth to memory;   calculating an acceleration enrichment pulsewidth value; and   storing the said pulsewidth value to a fuel pulsewidth in order to control a fuel injector.